Epidemiology 7/8 Flashcards
what does the P value mean
probability of getting a result as extreme or more extreme if the null hypothesis is true (i.e.. no difference)
when do we reject null hypothesis
P less than or equal to 0.05
T/F: P values measure how likely study hypothesis is true
FALSE
What is a confidence interval
a range of values that could be plausibly generated by the sample
When you want to be more “confident” what occurs with the confidence interval?
It gets wider so you can capture the true value more often
define sensitivity
how well does a test correctly identify those with a disease (TP/all with disease)
specificity
how well a test correctly identifies those WITHOUT a disease (TN/all without disease)
PPV
of those that test positive, what proportion actually have disease
NPV
of those who test negative, what proportion actually don’t have the disease
What happens to sensitivity/specificity/PPV/NPV when prevalence changes
Sensitivity/specificity don’t change
- PPV increases with increasing prevalence, decreases with decreasing prevalence
- NPV decreases with increasing prevalence and increases with decreasing prevalence
Receiver Operating characteristic
describes intrinsic accuracy of a test considering various threshold changes
- larger area under curve indicates greater discriminating ability of test
number needed to treat/screen (NNT/NNS)
what is the impact of the treatment
- number of ppl you need to treat/screen to prevent 1 bad outcome
What does a higher NNT mean
increased number needed to treat = less effective test
Case-control study
select ppl with/without disease or outcome. Compared with controls regarding past exposures
Cohort study
select ppl with exposure/not but are initially free of the outcome. Followed and assess incidence of outcome in both exposure groups
